Certain optical systems, such as projection systems and automobile headlights, require light sources with high radiance or luminance. Until recently, the luminance of conventional light emitting diodes (LEDs) was inadequate to fulfill the needs for such applications. However, even with current high performance LEDs, the radiance requirement for some optical systems is difficult to fulfill. By way of example, optical systems that require polarized light and use conventional (randomly polarized) LEDs typically suffer a loss in radiance making such system unacceptable for high brightness applications. Additionally, systems that convert the wavelengths of light emitted from a high radiance LED, e.g., using a phosphor, lose radiance and are therefore similarly unacceptable for high brightness applications.
Thus, what is needed is an optical system that uses LEDs and that provides sufficient radiance to be used in high brightness applications.